\RequirePackage{cancel}
\RequirePackage{shuffle}

\newcommand{\ra}{\rightarrow}

\newcommand{\Ra}{\Rightarrow}

\newcommand{\la}{\leftarrow}

\newcommand{\La}{\Leftarrow}

\newcommand{\Llra}{\Longleftrightarrow}
\newcommand{\lra}{\leftrightarrow}

\newcommand{\seq}{\geqslant}

\newcommand{\ieq}{\leqslant}

\newcommand{\fan}{\forall n \seq 0}

\newcommand{\vabs}[1]{\left|#1\right|}

\newcommand{\der}[2][\option]{
    \def\option{\mbox{}}
    \ensuremath{\frac{\mathrm{d}\option}{\mathrm{d}#2}}
}

\let\sumOld\sum
\renewcommand{\sum}{\displaystyle\sumOld}

\newcommand{\sumn}{\sum_{n\seq 0}}

\let\minOld\min
\renewcommand{\min}{\displaystyle\minOld}

\let\maxOld\max
\renewcommand{\max}{\displaystyle\maxOld}

\let\supOld\sup
\renewcommand{\sup}{\displaystyle\supOld}

\let\infOld\inf
\renewcommand{\inf}{\displaystyle\infOld}

\let\prodOld\prod
\renewcommand{\prod}{\displaystyle\prodOld}

\let\bigcapOld\bigcap
\renewcommand{\bigcap}{\displaystyle\bigcapOld}

\let\bigcupOld\bigcup
\renewcommand{\bigcup}{\displaystyle\bigcupOld}

\let\limOld\lim
\renewcommand{\lim}{\displaystyle\limOld}

\let\epsiOld\epsilon
\let\varepsiOld\varepsilon
\renewcommand{\epsilon}{\varepsilon}

\let\fracOld\frac
\renewcommand{\frac}[2]{\displaystyle\fracOld{#1}{#2}}

\renewcommand{\varepsilon}{\epsiOld}

\let\phiOld\phi
\renewcommand{\phi}{\varphi}

\renewcommand{\varphi}{\phiOld}

\newcommand{\nat}{\mathbb{N}}
\newcommand{\reel}{\mathbb{R}}
\newcommand{\zent}{\mathbb{Z}}

\newcommand{\limn}{\lim_{n\ra\infty}}